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Aluminum NJ or F-shape Parapets

Question
State IL
Description Text

I am the IDOT Planning Unit Chief for the Bureau of Bridges
and Structures in Springfield, Illinois.  We have a few of these aluminum
shapes parapets on truss bridges within the state.  We are preparing to
rehabilitate one of these trusses.  The posts of this parapet need to be
replaced due steel deterioration in the lower portion of the posts.  The
consultant has indicated to me that the existing post connection is very weak
and would not satisfy typical test level criteria.  I would like to meet a
minimum TL-3 safety level after the rehabilitation of this bridge. 



I researched the various web sites for TL data on these
types of barriers and did not find much.  Would you be able to direct me
to a site that has this barrier and TL equivalent safety level or similar?

Keywords
  • Bridge Rails
Other Keywords none
Date January 21, 2014


Response
Response

I am aware of two websites that may have materials which may be helpful. First, the AASHTO Task Force 13 Committee has been slowly working on updating an online bridge railing guide. Subcommittee No. 3 volunteers have been trying to review the original materials and slowly add new materials. I have provided a link to the page, including a few pages for aluminum rails that are included for now but may change as the review process continues. Please let me know if you have questions about this website.

 

https://www.aashtotf13.org/Bridge-Rail.php

 

http://guides.roadsafellc.com/bridgeRailGuide/index.php?action=browse

 

http://guides.roadsafellc.com/bridgeRailGuide/index.php?action=view&railing=4

 

Next, I am providing a link to FHWA’s bridge railing site. You may find some interesting information here.

 

http://safety.fhwa.dot.gov/roadway_dept/policy_guide/road_hardware/barriers/bridgerailings/index.cfm

 

Finally, I am providing a link to FHWA’s list of accepted longitudinal barriers, which has some bridge rails included. One would need to search through the posted items.

 

http://safety.fhwa.dot.gov/roadway_dept/policy_guide/road_hardware/barriers/index.cfm

 

Can you provide details for the existing aluminum railing system so that I know what you are seeking to repair/replace.

 

Ron

Date January 21, 2014
Attachment b132.pdf
Attachment F350 Intro V3.pdf
Attachment FshapeBR_IJCrash.pdf
Attachment img-Z30075419-0001.pdf
Attachment img-Z30075442-0001.pdf


Response
Response

Thank you for your reply and reference website locations. 

The post and connection to the deck system warrants our concern with the proposed rehabilitation since we plan to reconnect the existing aluminum barrier based on the high cost and good condition of this barrier. 

I attached the details of the barrier and connections for your information.  We need to provide an attachment for a typical bridge deck and a concrete-filled steel grid deck as indicated by the drawings.

The existing aluminum barrier is an older design with different connections that probably do not correlate to the testing in the attached documents.  It may be difficult to demonstrate the existing barrier would satisfy TL-3.

Thanks again for the information,

 

Tim Craven

Date January 21, 2014


Response
Response I have briefly reviewed your details. The aluminum system is really too complex to analyze via hand calculations. To evaluate the capacity of the system to meet Test Level 3 of NCHRP 350, one would likely need to perform 1 of 2 operations – (1) utilize FEA in combination with some limited dynamic component testing to determine capacities for connections and components or (2) construct the railing and anchorage system and conduct full-scale testing with a pickup truck.

Your system is similar to the system I noted below. I have gone to the AASHTO TF13 website to download a few files. They are attached. FHWA approved an alternative configuration several years ago. For your system, some of my concerns pertain to the post-to-deck anchorage capacity as well as the anchorage for the front barrier base. In addition, it is unknown for now as to the local crush resistance of the aluminum space truss as well as weakened regions nears joints. I believe that one of the two options would be needed to explore the capacity of this existing aluminum bridge railing system.

As such, I do not have a good answer right now to suggest or inform you that the system will meet TL-3 of NCHRP 350. Let me know if you want to further discuss this matter. 
Date January 22, 2014


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